A public-key signature scheme employs two mathematically linked keys—a public key and a private key. A user may generate a public/private key pair with relative ease, publish the public key, and keep the private key secret. The user may digitally sign messages by generating digital signatures of the messages using the private key. Anyone with the public key may verify the authenticity of a message by verifying the message and the associated digital signature using the public key.
People may receive identification numbers, such as a passport number, an identification card number, a social security number, a bank account number, or an insurance policy number, etc., from government agencies and other authorities. Similarly, employees may receive identification information, such as an employee number, or an employee user ID, etc., from employers. However, it is uncommon for government agencies, various authorities, or employers to issue public/private key pairs usable in a public-key signature scheme.